Contents

Production

In Northern
Europe, the word "tar" refers primarily to a substance that is
derived from the wood
and roots of pine. In earlier
times it was often used as a water repellent coating for boats,
ships, and roofs. It is still used as an additive in the flavoring
of candy, alcohol and other foods. Wood tar is microbicidal and has a
pleasant odor — a sweet musky scent much like that of barbecue.
Producing tar from wood was known in ancient Greece, and has
probably been used in Scandinavia since the iron age. For
centuries, dating back at least to the 14th century, tar was among
Sweden's most important
exports. Sweden exported 13,000 barrels of tar in 1615 and 227,000 barrels in the peak year of 1863. Production nearly stopped in
the early 20th century, when other chemicals replaced tar and
wooden ships were replaced by steel ships.

The heating (dry distilling) of pine wood causes tar and pitch to drip away from the wood and
leave behind charcoal. Birchbark is used to make particularly fine
tar, known as "Russian oil", suitable for leather protection. The
by-products of wood tar are turpentine and charcoal. When deciduous tree woods are
subjected to destructive distillation the products are methanol (wood alcohol) and
charcoal.

Tar kilns (Swedish: tjärdal,
Norwegian: tjæremila, Finnish: tervamiilu) are
dry distillation ovens, historically used in Scandinavia for producing tar from wood.
They were built close to the forest, from limestone or from more
primitive holes in the ground. The bottom is sloped into an outlet
hole, to allow the tar to pour out. The wood is split to dimensions
of a finger and stacked densely, and finally covered tight with
dirt and moss. If oxygen can enter, the wood might catch fire, and
the production would be ruined. On top of this, a fire is stacked
and lit. After a few hours, the tar starts to pour out, and
continues to do so for a few days.

Uses

Tar was used as seal for roofing shingles and to seal the hulls of ships and boats. For millennia wood tar was used to
waterproof sails and boats, but
today sails made from inherently waterproof synthetic substances
have negated the need for tar. Wood tar is still used to seal
traditional wooden boats and the roofs of historical shingle-roofed
churches, as well as painting exterior walls of log buildings. Tar
is also a general disinfectant.

In Finland wood tar was
once considered a panacea reputed to heal "even those
cut in twain through their midriff". A Finnish proverb states that
if sauna, vodka and tar won't help, the disease is
fatal. Wood tar is used in traditional Finnish medicine
because of its microbicidial properties.

Wood tar is also available diluted as tar water, which has
numerous uses:

As a flavoring for candies (e.g. Terva Leijona) and alcohol (Terva
Viina)

As a spice for food, like meat

As a scent for saunas. Tar
water is mixed into water which is turned into steam in the
sauna

Mixing tar with linseed
oilvarnish produces tar
paint. Tar paint has a translucent brownish hue, and can be used to
saturate and tone wood and protect it from weather. Tar paint can
also be toned with various pigments, producing translucent colours
and preserving the wood texture.

Other types
of tar

A tar-like substance can be produced from corn stalks by heating in
a microwave. This process is known as pyrolysis.

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Term
misuse

The word "tar" is often used to describe several distinct
substances which are not actually tar. Naturally occurring "tar pits" (e.g. the La Brea Tar
Pits in Los
Angeles) actually contain asphalt rather than tar. Tar sand deposits contain
various mixtures of sand (or rock) with bitumen or heavy crude oil and not tar, as does
the Tar Tunnel in Shropshire. "Rangoon
tar", also known as "Burmese Oil" or "Burmese Naphtha", is actually
petroleum. "Tar" and "pitch" are
sometimes used interchangeably; however, pitch is considered more
solid while tar is more liquid.

Coal

In English, German, and French, "tar" is a substance primarily
derived from coal. It was formerly one of the products of gasworks. Tar made from coal
or petroleum is considered toxic and carcinogenic because
of its high benzene content,
though coal tar in low
concentrations is used as a topical medicine. Coal and petroleum tar has a
pungent odor.

From LoveToKnow 1911

TAR, a product of the destructive distillation of
organic substances. It is a highly complex material, varying in its
composition according to the nature of the body from which it is
distilled, - different products, moreover, being obtained according
to the temperature at which the process of distillation is carried
on. As commercial products there are two principal classes of tar
in use - (1) wood tar, the product of the special distillation of
several varieties of wood, and (2) coal tar, which is primarily a by-product of
the distillation of coal during
the manufacture of gas for
illuminating purposes.. These tars are intimately related to bitumen, asphalt, mineral pitch and petroleum.

Wood Tar. - Wood tar, known also as Stockholm and as Archangel tar, is
principally prepared in the great pine forests of central and northern Russia, Finland and Sweden. The material chiefly employed is the
resinous stools and roots of the Scotch fir (Pinus sylvestris) and the Siberian larch (Larix sibirica),
with other less common fir-tree
roots. A large amount of tar is also prepared from the roots of the
swamp pine australis) in North and South Carolina,
Georgia and Alabama, in the United States. In the
distillation of wood a series of products, including gas, tar,
pyroligneous acid, acetone, wood spirit (see
Methyl Alcohol) and charcoal may be obtained, and any of these may
be the primary object of the operation.

The carbonization of wood can be effected in two ways: (I) by
stacking and firing as in the manufacture of charcoal: this method
is very wasteful as it is impossible to recover the valuable
byproducts; and (2) by distilling from retorts, ovens or kilns
(after the manner of coke
production from coal): this method is more economical as it leads
to the isolation of all the by-products. The retorts may be
horizontal or vertical and the heating effected by any available fuel, or by the inflammable gases and
less valuable grades of tar obtained in previous operations. The
condensing plant is also of variable design; a common pattern
consists of a connected series of slightly inclined copper pipes contained in a
rectangular tank of water (see Coal Tar). After settling the
distillate separates into three layers: the lowest consists chiefly
of tar and creosote oils with a
little acetic acid;
the middle layer consists of water, containing pyroligneous acid,
wood spirit, acetone with a little tarry matter; whilst the upper
consists of light hydrocarbons. The tarry layer is run off by means
of a cock near the base of the tank, and is then distilled from
retorts resembling coal tar stills. At first, between 110° and 120°
C., water and acetic acid comes over; then, between 120° - 230° C.,
the heavy or creosote oils; the residue in the still is wood pitch, which finds
application in making briquettes, artificial asphalts, certain
varnishes, &c. The crude tar and pitch are also largely used as
protective coatings for woodwork exposed to atmospheric conditions.
The heavy oils on further fractional distillation yield more acetic
acid, and then mixtures of carbolic acid, creosols, &c.

Wood tar is a semi-fluid substance, of a dark brown or black
colour, with a strong pungent odour and a sharp taste. Owing to the
presence of acetic acid, it has an acid reaction; it is soluble in
that acid, as well as in alcohol and the fixed and essential oils,
&c. Some varieties of tar have a granular appearance, from the
presence of minute crystals of pyrocatechin, which dissolve and disappear
on heating the substance.

Wood tar is used in medicine under the name of Fix
liquida. Its preparation unguentum picis liquidae is
composed of wood tar and yellow beeswax. Externally tar is a
valuable stimulating dressing in scaly skin diseases, such as psoriasis and chronic eczema. Internally wood tar is a
popular remedy as an expectorant in subacute and chronic bronchitis. It is usually
given as tar water, part of wood tar being stirred into 4 parts of
water and filtered. Given internally tar is likely to upset the
digestion; taken in large quantities it causes pain and vomiting and dark urine, symptoms similar
to carbolic acid poisoning.

Coal tar is used in medicine as Pix liquida preparata.
From it is made Liquor picis carbonis, prepared with tincture of quillaia. Coal
tar is rarely prescribed for internal use. Its external use is
similar to that of wood tar: the Liquor carbons detergens,
a proprietary preparation, owes its properties chiefly to the
contained phenol. It is used in water as a lotion for skin
diseases, and also in an inhaler in the treatment of whooping-cough,
croup and bronchitis.

The English used in this article or section may not be easy for everybody to understand.You can help Wikipedia by making this page or section simpler.

.]]

Tar is a viscous black liquid. It is made by the destructive distillation of organic matter. Most tar is produced from coal as a byproduct of coke production, but it can also be produced from petroleum, peat or wood.

Contents

Types of tar

Term misuse

The word "tar" is often used to describe several different substances which are not actually tar. Naturally occurring "tar pits" (e.g. the La Brea Tar Pits in Los Angeles) actually contain asphalt rather than tar. Tar sand deposits contain various mixtures of sand (or rock) with bitumen or heavy crude oil and not tar, as does the Tar Tunnel in Shropshire. "Rangoon tar", also known as "Burmese Oil" or "Burmese Naphtha", is actually petroleum. "Tar" and "pitch" are sometimes used interchangeably; however, pitch is considered more solid while tar is more liquid.

Coal

In English, German and French, "tar" is a substance primarily made from coal. It used to be one of the products of gasworks. Tar made from coal or petroleum is considered toxic. It causes cancer because of its high benzene content. In low concentrations, however, coal tar is used as a topical medicine. Coal and petroleum tar has a pungent odor.

Coal tar is listed at number 1999 in the United Nations list of dangerous goods.

Wood

Main page: pine tar

, Sweden.]]
In Northern Europe, the word "tar" refers primarily to a substance that is derived from the wood and roots of pine. In earlier times it was often used as a water repellent coating for boats, ships, and roofs. It is still used as an additive in the flavoring of candy, alcohol and other foods. Wood tar is microbicidal and has a pleasant odor. Producing tar from wood was known in ancient Greece, and has probably been used in Scandinavia since the Iron Age. For centuries, dating back at least to the 14th century, tar was among Sweden's most important exports. Sweden exported 13,000 barrels of tar in 1615 and 227,000 barrels in the peak year of 1863. Production nearly stopped in the early 20th century, when other chemicals replaced tar and wooden ships were replaced by steel ships.

The heating (dry distilling) of pine wood causes tar and pitch to drip away from the wood and leave behind charcoal. Birchbark is used to make particularly fine tar, known as "Russian oil", suitable for leather protection. The by-products of wood tar are turpentine and charcoal. When deciduous tree woods are subjected to destructive distillation the products are methanol (wood alcohol) and charcoal.

Tar kilns (Swedish: tjärdal, Norwegian: tjæremila) are dry destillation ovens, historically used in Scandinavia for producing tar from wood. They were built close to the forest, from limestone or from more primitve holes in the ground. The bottom is sloped into an outlet hole, to allow the tar to pour out. The wood is split to dimensions of a finger and stacked densely, and finally covered tight with dirt and moss. If oxygen can enter, the wood might catch fire, and the production would be ruined. On top of this, a fire is stacked and lit. After a few hours, the tar starts to pour out, and continues to do so for a few days.

Uses

Tar is used in treatment of the skin disease psoriasis, where coal tar is the most effective. Tar is also a general disinfectant. Petroleum tar was also used in ancient Egyptianmummification circa 1000 BC.[1]

Tar was a vital component of the first sealed, or "tarmac", roads. The streets of Baghdad were the first to be paved with tar from the 8th century AD.[1] It was also used as seal for roofing shingles and to seal the hulls of ships and boats. For millennia wood tar was used to waterproof sails and boats, but today sails made from inherently waterproof synthetic substances have negated the need for tar. Wood tar is still used to seal traditional wooden boats and the roofs of historical shingle-roofed churches, as well painting exterior walls of log buildings.

In Finland wood tar was once considered a panacea reputed to heal "even those cut in twain through their midriff". A Finnish proverb states that if sauna, vodka and tar won't help, the disease is fatal. Wood tar is used in traditional Finnish medicine because of its microbicidial properties.

Wood tar is also available diluted as tar water, which has numerous uses:

As a flavoring for candies (e.g. Terva Leijona) and alcohol (Terva Viina)

As a spice for food, like meat

As a scent for saunas. Tar water is mixed into water that is turned to steam to the air

Mixing tar with linseed oil varnish produces tar paint. Tar paint has a translucent brownish hue, and can be used to saturate and tone wood and protect it from weather. Tar paint can also be toned with various pigments, producing translucent colours and preserving the wood texture. Because of its paint-like properties, tar should not be touched with bare hands or feet, as it can dry to produce a permanent stain. However, in any case, paint thinner is used to remove it.